The origin of the word biomagnetism is unclear, but seems to have appeared several hundred years ago, linked to the expression animal magnetism. The present scientific definition took form in the 1970s, when an increasing number of researchers began to measure the magnetic fields produced by the human body. The first valid measurement was actually made in 1963. Now plant biomagnetism has been little studied. Searching for magnetic fields produced by plants may sound strange, but physicists at the University of California, Berkeley, are seriously looking for biomagnetism in plants using some of the most sensitive magnetic detectors available.
In an article that appeared this week in the Journal of Applied Physics, the UC Berkeley scientists describe the instruments they used to look for minuscule magnetic fields around a titan arum â€“ the world's largest flower â€“ during its brief bloom, the interference from local BART trains and traffic that bedeviled the experiment, and their ultimate failure to detect a magnetic field.
They established, however, that the plant generated no magnetic field greater than a millionth the strength of the magnetic field surrounding us here on Earth.
Bioelectromagnetism refers to the electrical, magnetic or electromagnetic fields produced by living cells, tissues or organisms. Examples include the cell membrane potential and the electric currents that flow in nerves and muscles, as a result of action potentials. Bioelectromagnetism is somewhat similar to bioelectromagnetics, which deals with the effect on life from external electromagnetism; yet such an effect also falls under the definition of bioelectromagnetism.
"There is a lot of activity now by scientists studying biomagnetism in animals, but not in plants," said Dmitry Budker, UC Berkeley professor of physics. "It is an obvious gap in science right now."
Bioelectromagnetism is studied primarily through the techniques of electrophysiology. In the late eighteenth century, the Italian physician and physicist Luigi Galvani first recorded the phenomenon while dissecting a frog at a table where he had been conducting experiments with static electricity. Galvani coined the term animal electricity to describe the phenomenon, while contemporaries labeled it galvanism. Galvani and contemporaries regarded muscle activation as resulting from an electrical fluid or substance in the nerves.
Bioelectromagnetism seems to be an aspect of all living things, including all plants and animals. Some animals have acute bioelectric sensors, and others, such as migratory birds, are believed to navigate in part by orienteering with respect to the Earth's magnetic field. Also, sharks are more sensitive to local interaction in electromagnetic fields than most humans. Other animals, such as the electric eel, are able to generate large electric fields outside their bodies.
"We feel like this is a first step in an interesting direction that we would like to pursue," he added.
Magnetic noise in the laboratory initially led the Budker team to the University of California Botanical Garden, which provided an isolated space for them to test their magnetometers. There, the researchers, including graduate student Eric Corsini, encountered the garden's famed titan arum (Amorphophallus titanium), a plant that every few years sends up a tall, thick stalk covered with thousands of small flowers enveloped by one large, flower-like calyx. During its brief flowering, the plant gives off a powerful odor of rotting flesh to attract the carrion beetles and flesh flies that pollinate it.
"This giant, skirt-like thing opens fairly quickly, over an hour or two, and the plant starts to heat up and get really warm, and then gives off this odor that is strongest for the first 12 hours," said Paul Licht, director of the UC Botanical Garden. "By the end of 24 hours, all the real action is over; the pollination cycle has a very brief window to succeed."
Because magnetic fields are created by moving electrical charges, such as a current of electrons, the researchers thought that rapid processes in the plant during the rapid heating might involve flowing ions that would create a magnetic field. In the titan arum, the rapid heating raises the plant temperature as high as 20 to 30 Celsius (70-85 degrees Fahrenheit).
"In principle, there shouldn't be a fundamental difference between animals and plants in this respect, but as for which plants might produce the highest magnetic fields, that is a question for biologists," Budker said.
In June 2009, one of the garden's arums was ready to erupt, so the Budker group, headed by Corsini, set up a sensitive, commercial magnetometer next to the plant in a hothouse and monitored it continually. During the day, visitors entering the hothouse generated magnetic signals, and the BART trains several miles away created .05 microtesla signals periodically. Whatever the plant put out could not be readily measured.
For further information: http://www.eurekalert.org/pub_releases/2011-04/uoc--ipg040711.php